The flooding of the the San Matías Gulf: the Northern Patagonia sea-level curve

ISLA, F.

GEOMORPHOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 203 p. 60 - 65

0169-555X

Northern Patagonia is characterised by tectonic depressions below present sea level. Some of them are today flooded by the sea; others remain emerged although they are at altitudes of -50 m (Bajo del Gualicho), -35 m (Salinas Grandes) and -7 m (Salina La Piedra). San Matías Gulf was also an emergent depression below contemporary mean sea level during the Late Pleistocene. It was flooded between 11,500 and 11,000 years ago, when the sea level surpassed the sill of the gulf (today 50 m below mean sea level) during the second postglacial sea-level jump (meltwater pulse1b). In-situ pieces of wood dredged from the bottom of the gulf at depths of 70 m gave a conventional age of 11,310 ± 150 years BP. In those days, shrublands extended on the slopes of the tectonic depression. We used the wood, together with dated shells from the continental shelf, and shells and organic matter dated from the San Blas, Negro and Chubut coastal plains to construct a sea-level curve. The rise surpassed present level before 6,000 years BP reaching a maximum stand of +6 m, and then taking a gently falling trend towards present sea level.